Dryer

ABSTRACT

A dryer includes a tubular portion, an axial flow impeller located inside the tubular portion, a motor, a heater support portion positioned forward of the axial flow impeller inside the tubular portion, and a heater. The axial flow impeller includes a plurality of blades arranged in a circumferential direction. The heater support portion includes a plurality of plate-shaped portions extending radially outward from the blowing axis in a cross-section perpendicular or substantially perpendicular to the blowing axis. The number of positions at which circumferential positions of radially outer ends of the second edges of the blades and circumferential positions of the plate-shaped portions overlap with each other is always one or less regardless of a rotational position of the axial flow impeller.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a dryer.

2. Description of the Related Art

Dryers designed to dry or heat objects by blowing hot air are known.Such a known dryer is described, for example, in JP-A 6-125810. A hairdryer described in JP-A 6-125810 includes a tubular body case elongatedin a front-rear direction, a fan, a motor, flow control vanes, and aheater. The fan, the motor, the flow control vanes, and the heater arecontained in the body case. The heater is wrapped across outercircumferences of radially extending plates arranged to extend in aradial manner from an outer circumference of an inner insulation tube(see paragraph [0009] of JP-A 6-125810).

In order to increase the volume of air sent by a dryer, it is necessaryto rotate a fan of the dryer at a higher speed. However, in the hairdryer described in JP-A 6-125810, for example, a large number ofmembers, such as the flow control vanes, the heater, and the radiallyextending plates, are arranged downstream of the fan inside the bodycase. This hair dryer has a problem in that, if the fan is rotated at ahigh speed, a large amount of noise is caused by interference of theairflow generated by the fan with other members.

SUMMARY OF THE INVENTION

A dryer according to a preferred embodiment of the present invention isa dryer configured to send hot air forward along a blowing axisextending in a front-rear direction. The dryer includes a tubularportion extending in an axial direction around the blowing axis; anaxial flow impeller located inside the tubular portion; a motorconfigured to rotate the axial flow impeller about the blowing axis or arotation axis extending parallel or substantially parallel to theblowing axis; a heater support portion positioned forward of the axialflow impeller inside the tubular portion; and a heater supported by theheater support portion inside the tubular portion. The axial flowimpeller includes a plurality of blades positioned in a circumferentialdirection. The heater support portion includes a plurality ofplate-shaped portions extending radially outward from the blowing axisin a cross-section perpendicular or substantially perpendicular to theblowing axis. Both circumferential edges of each blade include a firstedge and a second edge positioned forward of the first edge with respectto a direction parallel to or substantially parallel to the blowingaxis. The number of positions at which circumferential positions ofradially outer ends of the second edges of the blades andcircumferential positions of the plate-shaped portions overlap with eachother is always one or less regardless of a rotational position of theaxial flow impeller.

According to the above preferred embodiment of the present invention, anairflow which is sent forward from the radially outer end of the secondedge of each blade does not strike two or more of the plate-shapedportions at the same time. Thus, noise caused by interference of theairflow with any plate-shaped portion is significantly reduced orprevented.

The above and other elements, features, steps, characteristics andadvantages of the present invention will become more apparent from thefollowing detailed description of the preferred embodiments withreference to the attached drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a vertical cross-sectional view of a dryer according to apreferred embodiment of the present invention.

FIG. 2 is a cross-sectional view of the dryer taken along a planeindicated by line A-A in FIG. 1 and as viewed from a direction indicatedby arrows A.

FIG. 3 is a cross-sectional view of the dryer taken along a planeindicated by line B-B in FIG. 1 and as viewed from a direction indicatedby arrows B.

FIG. 4 is a cross-sectional view of the dryer taken along a planeindicated by line C-C in FIG. 1 and as viewed from a direction indicatedby arrows C.

FIG. 5 is a cross-sectional view of a dryer according to an examplemodification of the above preferred embodiment of the present inventiontaken at the same position and as viewed from the same direction as thecross-sectional view of FIG. 4.

FIG. 6 is a cross-sectional view of a dryer according to an examplemodification of the above preferred embodiment of the present inventiontaken at the same position and as viewed from the same direction as thecross-sectional view of FIG. 4.

FIG. 7 is a cross-sectional view of a dryer according to an examplemodification of the above preferred embodiment of the present inventiontaken at the same position and as viewed from the same direction as thecross-sectional view of FIG. 4.

FIG. 8 is a cross-sectional view of a dryer according to an examplemodification of the above preferred embodiment of the present inventiontaken at the same position and as viewed from the same direction as thecross-sectional view of FIG. 4.

FIG. 9 is a cross-sectional view of a dryer according to an examplemodification of the above preferred embodiment of the present inventiontaken at the same position and as viewed from the same direction as thecross-sectional view of FIG. 4.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Hereinafter, preferred embodiments of the present invention will bedescribed with reference to the accompanying drawings. It is assumedherein that a “blowing axis” is defined along a direction in which adryer blows an airflow. It is also assumed herein that a directionparallel to or substantially parallel to the blowing axis is referred toby the term “axial direction”, “axial”, or “axially”, that directionsperpendicular or substantially perpendicular to the blowing axis arereferred to by the term “radial direction”, “radial”, or “radially”, andthat a direction along a circular arc centered on the blowing axis isreferred to by the term “circumferential direction”, “circumferential”,or “circumferentially”. It is also assumed herein that a downstream sideand an upstream side (with respect to the airflow) along the blowingaxis are defined as a front side and a rear side, respectively. Theshape of each member or portion and relative positions of differentmembers or portions will be described based on the above assumptions. Itshould be noted, however, that the above definitions of a front-reardirection and the front and rear sides are not meant to restrict in anyway the orientation of a dryer according to any preferred embodiment ofthe present invention when in use.

FIG. 1 is a vertical cross-sectional view of a dryer 1 according to apreferred embodiment of the present invention. FIG. 2 is across-sectional view of the dryer 1 taken along a plane indicated byline A-A in FIG. 1 and as viewed from a direction indicated by arrows A.FIG. 3 is a cross-sectional view of the dryer 1 taken along a planeindicated by line B-B in FIG. 1 and as viewed from a direction indicatedby arrows B. FIG. 4 is a cross-sectional view of the dryer 1 taken alonga plane indicated by line C-C in FIG. 1 and as viewed from a directionindicated by arrows C.

The dryer 1 is an apparatus designed to send hot air forward in theaxial direction by rotating an impeller 20 through power of a motor 30.The dryer 1 is preferably used, for example, as a household hair dryeror a hair dryer for professional use to dry hair. Note, however, thatdryers according to preferred embodiments of the present invention maybe dryers designed to dry or heat objects other than hair, e.g.,industrial dryers, heat guns, etc. Referring to FIG. 1, the dryer 1according to the present preferred embodiment preferably includes ahousing 10, the impeller 20, the motor 30, a flow control member 40, aheater support portion 50, and a heater 60. The impeller 20 is an axialflow impeller.

The housing 10 preferably includes a tubular portion 11 and a handleportion 12. The tubular portion 11 is arranged to surround a blowingaxis 9, and extends in the axial direction to assume a cylindrical orsubstantially cylindrical shape. The handle portion 12 extends radiallyoutward from a surface of the tubular portion 11. The tubular portion 11includes an air inlet at an axially rearward end thereof. A filter 711is preferably attached at the air inlet 71 to prevent dust fromintruding into an interior of the tubular portion 11. In addition, thetubular portion 11 includes an air outlet 72 at an axially forward endthereof.

Referring to FIGS. 2 to 4, the tubular portion 11 according to thepresent preferred embodiment is perfectly circular or substantiallyperfectly circular in a cross-section taken along any planeperpendicular to the blowing axis 9. Note, however, that the tubularportion 11 may alternatively be arranged to have any other desirableshape, such as, for example, an ellipse, a quadrilateral, etc., in thecross-section taken along any plane perpendicular to the blowing axis 9.In addition, according to the present preferred embodiment, the diameterof the tubular portion 11 is arranged to decrease in an axially forwarddirection. Note, however, that the diameter of the tubular portion 11may alternatively be arranged to be constant or to increase in theaxially forward direction. Also note that the shape of cross-sections ofthe tubular portion 11 taken along planes perpendicular to the blowingaxis 9 may be arranged to vary as the cross-section moves in the axiallyforward direction.

The impeller 20 is preferably a member configured to rotate about theblowing axis 9 to generate an air current traveling axially forward. Theimpeller 20 is located inside the tubular portion 11. Referring to FIGS.1 and 2, the impeller 20 according to the present preferred embodimentincludes a cup portion 21 arranged at a center thereof, and a pluralityof blades 22 extending radially outward from the cup portion 21. The cupportion 21 is fixed to a shaft 31 of the motor 30. The plurality ofblades 22 are positioned in a circumferential direction radially outsideof the cup portion 21. Each blade 22 preferably extends obliquely withrespect to both the axial direction and the circumferential direction.

Here, of both circumferential edges of each blade 22, a front-side edgeand a rear-side edge with respect to a rotation direction of theimpeller 20 are defined as a first edge 221 and a second edge 222,respectively. In this impeller 20, the second edge 222 is arrangedaxially forward of the first edge 221. Accordingly, once the impeller 20starts rotating, an airflow which travels axially forward from behindthe impeller 20 is generated.

The impeller 20 according to the present preferred embodiment ispreferably a single monolithic resin member obtained by an injectionmolding process. Note, however, that the impeller 20 may alternativelybe defined by a plurality of members. For example, the cup portion 21and the plurality of blades 22 may be defined by separate members. Alsonote that the impeller 20 may not necessarily be made of a resin.

The motor 30 is a mechanism arranged to supply, to the impeller 20,power for rotation. According to the present preferred embodiment, themotor 30 is arranged axially forward of the impeller 20. Note, however,that the motor 30 may alternatively be arranged axially rearward of theimpeller 20. The motor 30 includes the shaft 31, which extends along theblowing axis 9. Once the motor 30 is driven, a torque centered on theblowing axis 9 is produced through magnetic interaction between, forexample, coils and a magnet located inside the motor 30. The shaft 31 ofthe motor 30 is thus caused to rotate about the blowing axis 9.

The motor 30 according to the present preferred embodiment is preferablya brushless DC motor. The brushless DC motor has a longer life than acomparable brushed motor because the brushless DC motor is free fromdeterioration in performance which is caused by a brush wearing out. Inaddition, it is easier to change the speed of the brushless DC motorthan the speed of an AC motor, and it is also easier to reduce the powerconsumption of the brushless DC motor than the power consumption of theAC motor. Note, however, that a motor according to a preferredembodiment of the present invention may be any desirable motor, such as,for example, a brushed motor or an AC motor instead of a brushless DCmotor.

The flow control member 40 is preferably arranged axially forward of theimpeller 20 and axially rearward of the heater support portion 50 insidethe tubular portion 11. The flow control member 40 preferably includes aplurality of stationary vanes 41 extending radially or substantiallyradially. The stationary vanes 41 are positioned in the circumferentialdirection radially outside of the motor 30. The airflow generated by theimpeller 20 is sent toward the heater support portion 50 through gapsbetween the stationary vanes 41.

The heater support portion 50 is arranged axially forward of theimpeller 20, the motor 30, and the flow control member 40 inside thetubular portion 11. The heater support portion 50 preferably includesfour plate-shaped portions 51 extending in a radial manner with theblowing axis 9 as a center. Referring to FIG. 4, each of the fourplate-shaped portions 51 preferably extends radially outward from theblowing axis 9 in a straight or substantially straight line in across-section perpendicular or substantially perpendicular to theblowing axis 9.

According to the present preferred embodiment, the heater supportportion 50 is preferably defined by a combination of two support plates52. The two support plates 52 are preferably fixed to each other by, forexample, fitting cuts defined in both the support plates 52 to eachother. Each support plate 52 preferably includes a pair of plate-shapedportions 51 each of which extends in a mutually opposite direction fromthe blowing axis 9. Thus, the four plate-shaped portions 51 arepreferably arranged around the blowing axis 9 at angular intervals ofabout 90 degrees, for example. A reduction in the number of parts of theheater support portion 50 can be achieved by combining the supportplates 52 each of which includes the pair of plate-shaped portions 51 asdescribed above. Note, however, that each of the plate-shaped portions51 may be defined by a separate member.

The heater 60 is a heat source used to heat the airflow generated by theimpeller 20. A heating wire, such as a nichrome wire, which generatesheat when energized, for example, is preferably used as the heater 60.The heater 60 is located inside the tubular portion 11, and is supportedby the heater support portion 50. Specifically, the heater 60 ispreferably retained in cutouts defined in the plate-shaped portions 51.Note that the heater 60 may alternatively be wrapped around radiallyouter edges of the plate-shaped portions 51 such that the heater 60 isplaced across the four plate-shaped portions 51.

Once a power switch of the dryer 1 is turned on, electric current issupplied to both the motor 30 and the heater 60. The motor 30 is thusactivated to cause the shaft 31 and the impeller 20 fixed to the shaft31 to rotate about the blowing axis 9. As a result, gas is acceleratedby the blades 22, and an airflow traveling axially forward is generatedinside the tubular portion 11. The airflow, which is sent forward fromthe impeller 20 through the flow control member 40, is heated by heat ofthe heater 60. Then, the heated wind is blown forward out of the tubularportion 11 through the air outlet 72.

The dryer 1 has a structure designed to reduce noise caused byinterference of the airflow generated by the impeller 20 with the heatersupport portion 50. This structure will be described below withreference to FIG. 4. Note that, in FIG. 4, the impeller 20 as viewedfrom the front side in the axial direction is represented by brokenlines.

Referring to FIG. 4, the number of blades 22 of the impeller 20according to the present preferred embodiment is preferably five, forexample. Accordingly, the number of second edges 222 included in theimpeller 20 is also preferably five, for example. Gas which isaccelerated by each blade 22 is concentrated in a vicinity of a radiallyouter end 223 of the second edge 222 of the blade 22, and is sentaxially forward from the radially outer end 223. That is, the volume ofair which is sent axially forward from the vicinity of the radiallyouter end 223 of the second edge 222 is greater than the volume of airwhich is sent axially forward from any other portion of the blade 22.

Here, referring to FIG. 4, the circumferential position of an axiallyrearward end of each plate-shaped portion 51 is denoted by referencesymbol “Pa”, and the circumferential position of the radially outer end223 of the second edge 222 of each blade 22 is denoted by referencesymbol “Pb”. In this dryer 1, the circumferential positions Pa and thecircumferential positions Pb do not overlap with each other at more thanone position at any given time when viewed in the axial direction. Thatis, regardless of the rotational position of the impeller 20, the numberof positions at which the circumferential positions Pa and thecircumferential positions Pb overlap with each other is always one orless. Therefore, an airflow which is sent forward from the vicinity ofthe radially outer end 223 of the second edge 222 of each blade 22 doesnot strike two or more of axially rearward edges of the plate-shapedportions 51 at the same time. Thus, noise caused by interference of theairflow with any plate-shaped portion 51 is significantly reduced orprevented.

In addition, referring to FIG. 4, the circumferential position of aportion of the second edge 222 of each blade 22, the portion beingradially outward of a middle of the second edge 222 of the blade 22, isdenoted by reference symbol “Pb2”. Then, in this dryer 1, thecircumferential positions Pa and the circumferential positions Pb2 donot overlap with each other at more than one position at any given timewhen viewed in the axial direction. That is, regardless of therotational position of the impeller 20, the number of positions at whichthe circumferential positions Pa and the circumferential positions Pb2overlap with each other is always one or less. Therefore, not only theairflow which is sent forward from the vicinity of the radially outerend 223 of the second edge 222 of each blade 22, but also an airflowwhich is sent forward from the portion of the second edge 222 of eachblade 22, the portion being radially outward of the middle of the secondedge 222 of the blade 22, does not strike two or more of the axiallyrearward edges of the plate-shaped portions 51 at the same time. Thus,the noise caused by the interference of the airflow with anyplate-shaped portion 51 is further reduced or prevented.

It is assumed that Na denotes the number of plate-shaped portions 51included in the heater support portion 50. Then, Na is preferably fouraccording to the present preferred embodiment, for example. When Na isan even number, a pair of plate-shaped portions 51 can be defined by asingle support plate 52 as described above. However, if Na were two, thetwo plate-shaped portions 51 adjacent to each other would be arranged atangular intervals of 180 degrees, and it would be considerably difficultto place the heater 60 across the adjacent plate-shaped portions 51.Accordingly, according to the present preferred embodiment, Na ispreferably four as this is the smallest number that allows the heater 60to be easily supported by the support plates 52.

Meanwhile, it is assumed that Nb denotes the number of blades 22included in the impeller 20. Then, Nb is preferably five according tothe present preferred embodiment, for example. Thus, the number Na ofplate-shaped portions 51 included in the heater support portion 50 andthe number Nb of blades 22 included in the impeller 20 do not possesscommon denominators (except for one) and are not divisible with respectto one another. In addition, both the four plate-shaped portions 51 andthe five blades 22 are arranged at regular intervals in thecircumferential direction. If Na and Nb had a common divisor other thanone, the aforementioned circumferential positions Pa and theaforementioned circumferential positions Pb2 would overlap with eachother at more than one position at some moment. In addition, the totalof areas over which the blades 22 and the plate-shaped portions 51overlap with each other when viewed in the axial direction at a momentwhen the blades 22 and the plate-shaped portions 51 overlap with eachother most extensively would be large. When Na and Nb do not possesscommon denominators and are not divisible with respect to one another asin the present preferred embodiment, the total of the areas over whichthe blades 22 and the plate-shaped portions 51 overlap with each otherwhen viewed in the axial direction at the moment when the blades 22 andthe plate-shaped portions 51 overlap with each other most extensively isreduced. As a result, the noise caused by the interference of theairflow with any plate-shaped portion 51 is further reduced orprevented.

The dryer 1 according to the present preferred embodiment preferablyincludes the flow control member 40 between the impeller 20 and theheater support portion 50. Accordingly, the airflow generated by theimpeller 20 is subjected to flow control by the stationary vanes 41 ofthe flow control member 40, and is sent toward the heater supportportion 50. Thus, the noise caused by the interference of the airflowwith the heater support portion 50 is further reduced.

Here, as noted above, Pb denotes the circumferential position of theradially outer end 223 of the second edge 222 of each blade 22.Referring to FIG. 3, it is also assumed that Pc denotes thecircumferential position of an axially rearward edge of each stationaryvane 41. In this dryer 1, the circumferential positions Pb and thecircumferential positions Pc do not overlap with each other at more thanone position at any given time when viewed in the axial direction. Thatis, regardless of the rotational position of the impeller 20, the numberof positions at which the circumferential positions Pb and thecircumferential positions Pc overlap with each other is always one orless. Therefore, an airflow which is sent forward from the vicinity ofthe radially outer end 223 of the second edge 222 of each blade 22 doesnot strike two or more of the axially rearward edges of the stationaryvanes 41 at the same time. Thus, noise caused by interference of theairflow with any stationary vane 41 is reduced.

It is also assumed that Nc denotes the number of stationary vanes 41included in the flow control member 40. Then, Nc is preferably twelveaccording to the present preferred embodiment. Therefore, the number Nbof blades 22 included in the impeller 20 and the number Nc of stationaryvanes 41 included in the flow control member 40 do not possess commondenominators (except for one) and are not divisible with respect to oneanother. In addition, the twelve stationary vanes 41 are arranged atregular intervals in the circumferential direction. If Nb and Nc had acommon divisor other than one, the aforementioned circumferentialpositions Pb and the aforementioned circumferential positions Pc wouldoverlap with each other at more than one position at some moment. Inaddition, the total of areas over which the blades 22 and the stationaryvanes 41 overlap with each other when viewed in the axial direction at amoment when the blades 22 and the stationary vanes 41 overlap with eachother most extensively would be large. When Nb and Nc do not possesscommon denominators and are not divisible with respect to one another asin the present preferred embodiment, the total of the areas over whichthe blades 22 and the stationary vanes 41 overlap with each other whenviewed in the axial direction at the moment when the blades and thestationary vanes 41 overlap with each other most extensively is reduced.

In addition, according to the present preferred embodiment, the numberNc of stationary vanes 41, i.e., twelve, is preferably exactly threetimes the number Na of plate-shaped portions 51, i.e., four. When Nc isan integral multiple of Na as in the present preferred embodiment, it ispossible to arrange each of all the plate-shaped portions 51 to overlapwith one of the stationary vanes 41 when viewed in the axial direction.This leads to a reduction in the combined area of the stationary vanes41 and the plate-shaped portions 51 when viewed in the axial direction.Thus, noise caused by interference of the airflow with the stationaryvanes 41 and the plate-shaped portions 51 is further reduced orprevented.

While a preferred embodiment of the present invention has been describedabove, it will be understood that the present invention is not limitedto the above-described preferred embodiment.

FIG. 5 is a cross-sectional view of a dryer 1A according to an examplemodification of the above-described preferred embodiment taken at thesame position and as viewed from the same direction as thecross-sectional view of FIG. 4. In FIG. 5, an impeller 20A as viewedfrom the front side in the axial direction is represented by brokenlines. In the modification illustrated in FIG. 5, the number Na ofplate-shaped portions 51A included in a heater support portion 50A ispreferably four, for example. Meanwhile, the number Nb of blades 22Aincluded in the impeller 20A is preferably seven, for example.Therefore, Na and Nb do not possess common denominators (except for one)and are not divisible with respect to one another. In addition, both thefour plate-shaped portions 51A and the seven blades 22A are arranged atregular intervals in the circumferential direction. Thus, the total ofareas over which the blades 22A and the plate-shaped portions 51Aoverlap with each other when viewed in the axial direction at a momentwhen the blades 22A and the plate-shaped portions 51A overlap with eachother most extensively is reduced.

In addition, also in the modification illustrated in FIG. 5, thecircumferential positions Pa of axially rearward ends of theplate-shaped portions 51A and the circumferential positions Pb ofradially outer ends 223A of second edges 222A of the blades 22A do notoverlap with each other at more than one position at any given time whenviewed in the axial direction. That is, regardless of the rotationalposition of the impeller 20A, the number of positions at which thecircumferential positions Pa and the circumferential positions Pboverlap with each other is always one or less. Therefore, an airflowwhich is sent forward from a vicinity of the radially outer end 223A ofthe second edge 222A of each blade 22A does not strike two or more ofaxially rearward edges of the plate-shaped portions 51A at the sametime. Thus, noise caused by interference of the airflow with anyplate-shaped portion 51A is significantly reduced or prevented.

FIG. 6 is a cross-sectional view of a dryer 1B according to anotherexample modification of the above-described preferred embodiment takenat the same position and as viewed from the same direction as thecross-sectional view of FIG. 4. In FIG. 6, an impeller 20B as viewedfrom the front side in the axial direction is represented by brokenlines. In the modification illustrated in FIG. 6, the number Na ofplate-shaped portions 51B included in a heater support portion 50B ispreferably six, for example. Meanwhile, the number Nb of blades 22Bincluded in the impeller 20B is preferably five, for example. Therefore,Na and Nb are relatively do not possess common denominators (except forone) and are not divisible with respect to one another. In addition,both the six plate-shaped portions 51B and the five blades 22B arearranged at regular intervals in the circumferential direction. Thus,the total of areas over which the blades 22B and the plate-shapedportions 51B overlap with each other when viewed in the axial directionat a moment when the blades 22B and the plate-shaped portions 51Boverlap with each other most extensively is significantly reduced orprevented.

In addition, also in the modification illustrated in FIG. 6, thecircumferential positions Pa of axially rearward ends of theplate-shaped portions 51B and the circumferential positions Pb ofradially outer ends 223B of second edges 222B of the blades 22B do notoverlap with each other at more than one position at any given time whenviewed in the axial direction. That is, regardless of the rotationalposition of the impeller 20B, the number of positions at which thecircumferential positions Pa and the circumferential positions Pboverlap with each other is always one or less. Therefore, an airflowwhich is sent forward from a vicinity of the radially outer end 223B ofthe second edge 222B of each blade 22B does not strike two or more ofaxially rearward edges of the plate-shaped portions 51B at the sametime. Thus, noise caused by interference of the airflow with anyplate-shaped portion 51B is significantly reduced or prevented.

FIG. 7 is a cross-sectional view of a dryer 1C according to yet anotherexample modification of the above-described preferred embodiment takenat the same position and as viewed from the same direction as thecross-sectional view of FIG. 4. In FIG. 7, an impeller 20C as viewedfrom the front side in the axial direction is represented by brokenlines. In the modification illustrated in FIG. 7, the number Na ofplate-shaped portions 51C included in a heater support portion 50C ispreferably six, for example. Meanwhile, the number Nb of blades 22Cincluded in the impeller 20C is preferably seven, for example.Therefore, Na and Nb are relatively do not possess common denominators(except for one) and are not divisible with respect to one another. Inaddition, both the six plate-shaped portions 51C and the seven blades22C are arranged at regular intervals in the circumferential direction.Thus, the total of areas over which the blades 22C and the plate-shapedportions 51C overlap with each other when viewed in the axial directionat a moment when the blades 22C and the plate-shaped portions 51Coverlap with each other most extensively is reduced.

In addition, also in the modification illustrated in FIG. 7, thecircumferential positions Pa of axially rearward ends of theplate-shaped portions 51C and the circumferential positions Pb ofradially outer ends 223C of second edges 222C of the blades 22C do notoverlap with each other at more than one position at any given time whenviewed in the axial direction. That is, regardless of the rotationalposition of the impeller 20C, the number of positions at which thecircumferential positions Pa and the circumferential positions Pboverlap with each other is always one or less. Therefore, an airflowwhich is sent forward from a vicinity of the radially outer end 223C ofthe second edge 222C of each blade 22C does not strike two or more ofaxially rearward edges of the plate-shaped portions 51C at the sametime. Thus, noise caused by interference of the airflow with anyplate-shaped portion 51C is significantly reduced or prevented.

Note that, when the number of plate-shaped portions is six as itpreferably is in each of the modifications illustrated in FIGS. 6 and 7,the angular interval between adjacent ones of the plate-shaped portionsis smaller than in the case where the number of plate-shaped portions isfour, and therefore, a heater can be more stably supported across theadjacent plate-shaped portions.

FIG. 8 is a cross-sectional view of a dryer 1D according to yet anotherexample modification of the above-described preferred embodiment takenat the same position and as viewed from the same direction as thecross-sectional view of FIG. 4. In the modification illustrated in FIG.8, an impeller 20D preferably includes six blades 22D, for example.However, the six blades 22D are divided into three pairs of two blades,and the two blades 22D in each pair are arranged closer to each other inthe circumferential direction. Therefore, in the modificationillustrated in FIG. 8, spaces defined between circumferentially adjacentones of the blades 22D include smaller spaces and larger spaces. Thatis, the six blades 22D are arranged at irregular intervals in thecircumferential direction.

Also in the modification illustrated in FIG. 8, the circumferentialpositions Pa of axially rearward ends of plate-shaped portions 51D andthe circumferential positions Pb of radially outer ends 223D of secondedges 222D of the blades 22D preferably do not overlap with each otherat more than one position at any given time when viewed in the axialdirection. That is, regardless of the rotational position of theimpeller 20D, the number of positions at which the circumferentialpositions Pa and the circumferential positions Pb overlap with eachother is always one or less. Therefore, an airflow which is sent forwardfrom a vicinity of the radially outer end 223D of the second edge 222Dof each blade 22D does not strike two or more of axially rearward edgesof the plate-shaped portions 51D at the same time. Thus, noise caused byinterference of the airflow with any plate-shaped portion 51D ispreferably reduced.

Note that a pattern in which a plurality of blades are arranged atirregular intervals in the circumferential direction is not limited tothe pattern according to the modification illustrated in FIG. 8. Smallerspaces between circumferentially adjacent ones of the blades and largerspaces between circumferentially adjacent ones of the blades may bepositioned in a pattern different from that of the modificationillustrated in FIG. 8. Also note that circumferential spaces between aplurality of blades of an impeller may all be different in width.

FIG. 9 is a cross-sectional view of a dryer 1E according to yet anotherexample modification of the above-described preferred embodiment takenat the same position and as viewed from the same direction as thecross-sectional view of FIG. 4. Although the flow control member is notshown in each of FIGS. 4 to 8, a flow control member 40E is depictedaxially behind a heater support portion 50E in FIG. 9. In themodification illustrated in FIG. 9, the heater support portion 50Epreferably includes four plate-shaped portions 51E, and the flow controlmember 40E preferably includes twelve stationary vanes 41E, for example.Thus, the number of stationary vanes 41E is exactly three times thenumber of plate-shaped portions 51E. In addition, in the modificationillustrated in FIG. 9, an axially rearward edge of each of all theplate-shaped portions 51E overlaps at least in part with an axiallyforward edge 411E of one of the stationary vanes 41E. This leads to areduction in the combined area of the axially forward edges 411E of thestationary vanes 41E and the plate-shaped portions 51E when viewed inthe axial direction. In addition, the likelihood that an airflow whichis sent toward the heater support portion 50E through gaps between thestationary vanes 41E will strike any plate-shaped portion 51E isreduced. Thus, noise caused by interference of the airflow with thestationary vanes 41E and the plate-shaped portions 51E can be furtherreduced.

Note that, although the stationary vanes are arranged at regularintervals in the circumferential direction in each of theabove-described preferred embodiment and the modifications thereof, thestationary vanes may alternatively be arranged at irregular intervals inthe circumferential direction. Also note that the flow control membermay be omitted so that the heater support portion will be arrangedaxially forward of the impeller without the flow control memberintervening therebetween. In this case, the airflow generated by theimpeller will strike the heater support portion without being subjectedto flow control. Therefore, in this case, it is more important toarrange the blades and the plate-shaped portions in a positionalrelationship according to any of the above-described preferredembodiment and the modifications thereof, in order to reduce noisecaused by interference of the airflow with the heater support portion.

Each blade of the impeller according to each of the above-describedpreferred embodiment and the modifications thereof preferably is aso-called swept-forward blade, which is curved forward with respect tothe rotation direction of the impeller with increasing distance from theblowing axis. Note, however, that an impeller according to a preferredembodiment of the present invention may include so-called sweptbackblades, each of which is curved rearward with respect to the rotationdirection of the impeller with increasing distance from the blowingaxis. Also in the case of the sweptback blades, assuming that, of bothcircumferential edges of each blade, a front-side edge and a rear-sideedge with respect to the rotation direction of the impeller are definedas a first edge and a second edge, respectively, the second edge isarranged axially forward of the first edge.

In each of the above-described preferred embodiments and themodifications thereof, the impeller is configured to rotate about theblowing axis, and the plate-shaped portions of the heater supportportion are extending in the radial manner with the blowing axis as thecenter. Note, however, that a rotation axis of the impeller and acentral axis of the heater support portion may not necessarilycompletely coincide with each other. That is, as long as the blowingaxis is defined along the central axis of the heater support portion,the rotation axis of the impeller may be extending parallel orsubstantially parallel to the blowing axis at a position displaced fromthe blowing axis.

Preferred embodiments of the present invention and modifications thereofare applicable, for example, to dryers, blowers, heat guns, etc.

Note that the detailed shape of any member of the dryer may be differentfrom the shape thereof as illustrated in the accompanying drawings ofthe present application. Also note that features of the above-describedpreferred embodiment and the modifications thereof may be combinedappropriately as long as no conflict arises.

While preferred embodiments of the present invention have been describedabove, it is to be understood that variations and modifications will beapparent to those skilled in the art without departing from the scopeand spirit of the present invention. The scope of the present invention,therefore, is to be determined solely by the following claims.

What is claimed is:
 1. A dryer comprising: a tubular portion extending in an axial direction around a blowing axis; an axial flow impeller located inside the tubular portion; a motor configured to rotate the axial flow impeller about the blowing axis or a rotation axis extending parallel or substantially parallel to the blowing axis; a heater support portion positioned forward of the axial flow impeller inside the tubular portion; and a heater supported by the heater support portion inside the tubular portion; wherein the axial flow impeller includes a plurality of blades extending in a circumferential direction; the heater support portion includes a plurality of plate-shaped portions extending radially outward from the blowing axis in a cross-section perpendicular or substantially perpendicular to the blowing axis; both circumferential edges of each blade include a first edge and a second edge positioned forward of the first edge with respect to a direction parallel to or substantially parallel to the blowing axis; and a number of positions at which circumferential positions of radially outer ends of the second edges of the blades and circumferential positions of the plate-shaped portions overlap with each other is always one or less regardless of a rotational position of the axial flow impeller.
 2. The dryer according to claim 1, wherein a number of positions at which circumferential positions of portions of the second edges of the blades, each portion being radially outward of a middle of the second edge of the blade, and the circumferential positions of the plate-shaped portions overlap with each other is always one or less regardless of the rotational position of the axial flow impeller.
 3. The dryer according to claim 2, wherein both the plurality of blades and the plurality of plate-shaped portions are arranged at regular intervals in the circumferential direction; and a number of blades included in the axial flow impeller and a number of plate-shaped portions included in the heater support portion do not possess common denominators, except for one, and are not divisible with respect to one another.
 4. The dryer according to claim 2, further comprising a plurality of stationary vanes positioned forward of the axial flow impeller and rearward of the heater support portion, and positioned in the circumferential direction radially outside of the motor.
 5. The dryer according to claim 4, wherein a number of positions at which the circumferential positions of the radially outer ends of the second edges of the blades and circumferential positions of the stationary vanes overlap with each other is always one or less regardless of the rotational position of the axial flow impeller.
 6. The dryer according to claim 5, wherein both the plurality of blades and the plurality of stationary vanes are arranged at regular intervals in the circumferential direction; and a number of blades included in the axial flow impeller and a number of stationary vanes do not possess common denominators, except for one, and are not divisible with respect to one another.
 7. The dryer according to claim 6, wherein the number of stationary vanes is an integral multiple of a number of plate-shaped portions included in the heater support portion.
 8. The dryer according to claim 7, wherein an axially rearward edge of each of all the plate-shaped portions included in the heater support portion overlaps at least in part with an axially forward edge of one of the stationary vanes.
 9. The dryer according to claim 5, wherein a number of stationary vanes is an integral multiple of a number of plate-shaped portions included in the heater support portion.
 10. The dryer according to claim 9, wherein an axially rearward edge of each of all the plate-shaped portions included in the heater support portion overlaps at least in part with an axially forward edge of one of the stationary vanes.
 11. The dryer according to claim 1, wherein both the plurality of blades and the plurality of plate-shaped portions are arranged at regular intervals in the circumferential direction; and a number of blades included in the axial flow impeller and a number of plate-shaped portions included in the heater support portion are do not possess common denominators, except for one, and are not divisible with respect to one another.
 12. The dryer according to claim 11, wherein (Na, Nb)=(4, 5), (4, 7), (6, 5), or (6, 7), where Na denotes the number of plate-shaped portions included in the heater support portion and Nb denotes the number of blades included in the axial flow impeller.
 13. The dryer according to claim 1, further comprising a plurality of stationary vanes positioned forward of the axial flow impeller and rearward of the heater support portion, and positioned in the circumferential direction radially outside of the motor.
 14. The dryer according to claim 13, wherein a number of positions at which the circumferential positions of the radially outer ends of the second edges of the blades and circumferential positions of the stationary vanes overlap with each other is always one or less regardless of the rotational position of the axial flow impeller.
 15. The dryer according to claim 14, wherein both the plurality of blades and the plurality of stationary vanes are arranged at regular intervals in the circumferential direction; and a number of blades included in the axial flow impeller and a number of stationary vanes do not possess common denominators, except for one, and are not divisible with respect to one another.
 16. The dryer according to claim 15, wherein the number of stationary vanes is an integral multiple of a number of plate-shaped portions included in the heater support portion.
 17. The dryer according to claim 16, wherein an axially rearward edge of each of all the plate-shaped portions included in the heater support portion overlaps at least in part with an axially forward edge of one of the stationary vanes.
 18. The dryer according to claim 14, wherein a number of stationary vanes is an integral multiple of a number of plate-shaped portions included in the heater support portion.
 19. The dryer according to claim 18, wherein an axially rearward edge of each of all the plate-shaped portions included in the heater support portion overlaps at least in part with an axially forward edge of one of the stationary vanes.
 20. The dryer according to claim 1, wherein the plurality of blades are arranged at irregular intervals in the circumferential direction. 